Vacuum And Freeze-Up HVAC Sensor

ABSTRACT

An apparatus for monitoring an HVAC system. The apparatus comprises a freeze-up sensor, a vacuum sensor, and a thermostat. The freeze-up sensor communicates a signal to indicate that ice is developing in the HVAC system and the vacuum sensor communicates a signal to indicate that a vacuum pressure exists in the HVAC system. When a signal is detected, the apparatus deactivates the HVAC system to prevent damage. The thermostat comprises a touch-screen display with a continuous set-point.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/252,249 filed Oct. 16, 2009, the contents of which are incorporated fully herein by reference.

FIELD OF THE INVENTION

The present invention relates to thermostats and air conditioning units, and particularly to systems for monitoring the condition of the air conditioning units and preventing system failure.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus for monitoring a Heating, Ventilation, and Air Conditioning (HVAC) system. The HVAC system comprises a thermostat, a condensing unit, an evaporator coil, and a filter. The system comprises a freeze-up sensor, a receiver, a switch, and an indicator. The freeze-up sensor is located proximate the evaporator coil such that when the sensor detects a threshold temperature the sensor transmits a freeze-up signal. The receiver is for receiving the freeze-up signal. The switch is operatively connected to the HVAC system to disable the compressor and condensing unit after the freeze-up signal is received by the receiver. The indicator is located proximate the thermostat indicating receipt of the freeze-up signal by the receiver.

Another embodiment of the invention is directed to an apparatus for monitoring an HVAC system. The HVAC system comprises a thermostat, a condensing unit, an evaporator coil, and a filter. The apparatus comprises a freeze-up sensor located proximate the evaporator coil such that when the sensor detects a threshold temperature and condensation the freeze-up sensor transmits a freeze-up signal, a vacuum sensor located proximate the filter to transmit a vacuum signal upon detection of a vacuum pressure at or exceeding a threshold vacuum pressure, a receiver for receiving the freeze-up signal and the vacuum signal, a switch to disable the compressor and condensing unit after the receiver is receives the freeze-up signal or the vacuum signal, and an indicator located proximate the thermostat indicating the switch has disabled the compressor and condensing unit.

Still another embodiment of the invention is directed to a method for monitoring an HVAC system. The HVAC system comprises a thermostat, a condensing unit, a compressor, an evaporator coil, and a filter. The method comprises detecting a threshold temperature and condensation proximate the evaporator coil, transmitting a freeze-up signal after detection of the threshold temperature and condensation proximate the evaporator coil, receiving the freeze-up signal at a receiver, transmitting a shut-down signal to the compressor and condensing unit upon receipt of the freeze-up signal at the receiver, ceasing operation of the compressor and condensing unit after receiving the freeze-up signal, resuming operation of the compressor and condensing unit when the freeze-up signal is no longer received by the receiver.

Another embodiment is directed to a thermostat for use with an HVAC system comprising a filter. The thermostat comprises a touch screen display, a freeze-up sensor indicator located on the touch screen display and operatively connected to an freeze-up sensor, a vacuum sensor indicator located on the touch screen display and operatively connected to a vacuum sensor; wherein the freeze-up sensor indicator indicates the HVAC system is not operating due to a low temperature and condensation in the HVAC system and the vacuum sensor indicates the HVAC system is not operating due to a vacuum pressure in the HVAC system, and a continuous setpoint graph located at and adjustable on the touch screen display for creating a continuous temperature setpoint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is diagrammatic representation of an HVAC system for use with the apparatus for monitoring an HVAC system in accordance with the present invention.

FIG. 2 is diagrammatic representation of an inside unit and an apparatus for monitoring an HVAC system.

FIG. 3 is a diagrammatic representation of an outside unit and the apparatus for monitoring the HVAC system of FIG. 1.

FIG. 4 is a diagrammatic representation of a thermostat and thermostat display for use with an apparatus for monitoring the HVAC system of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Air conditioners, or HVAC systems, suffer from two problems which are addressed by the present invention. First, ice formation within an HVAC system causes multiple problems, including overheating a blower motor and pumping liquid Freon through the unit's compressor. Further, ice build-up can cause the HVAC system to operate at reduced efficiency. Second, clogged return air filters will restrict the flow of air into the HVAC system, which will cause the blower motor to work at a lower efficiency and limit the life of the motor. The present invention seeks to eliminate these two problems by utilizing sensors with a monitor in a system that can be read and operated by both owners and technicians. Further, the present invention allows limited operation of an HVAC system under ice build-up conditions to enable a building to be cooled when, for instance, occupants are away. Finally, ice build-up conditions can lead to a vacuum reading within an HVAC system and a clogged filter may lead to mild ice-up conditions. Therefore, there is a need for a thermostat which notes the first condition to arise so that an occupant or technician can know the origination of the problem with the HVAC system.

Turning to the drawings in general and FIG. 1 in particular, shown therein is an HVAC system 12. The HVAC system 12 comprises an outside unit 24 and an inside unit 26. The outside unit 24 may comprise a condenser 16 and a compressor 18. The outside unit 24 is generally located outside of a building, and is the equipment one thinks of when considering an air conditioner. The compressor 18 compresses refrigerant received from the inside unit 26 to raise its density and raise its temperature. The condenser 16 then uses the outside air to cool the dense refrigerant, often using a large fan (not shown) within the outside unit, condensing the pressurized vapor to a fluid. The inside unit 26 comprises a blower 20, an evaporator coil 14, and a filter 28. The filter 28 is adapted to remove dust and other impurities from air within a building. The blower 20 operates to move warm air from a building through the filter 28 and across the evaporator coil 14. The evaporator coil 14 is the primary heat exchange used for cooling a building. The evaporator coil 14 expands the condensed refrigerant fluid, causing the temperature to drop. The temperature of the coil 14 thus allows the air pushed across the coil by the blower 20 to cool. The thermostat 22 is operatively connected to the HVAC system 12 by a connection system 29 and may be located remote from the inside unit 24 and outside unit 26, at a location inside a building where a temperature set point can be initiated.

As shown by directional arrows in FIG. 1, the blower 20 causes air to be forced into the inside unit 26 through the filter 28. The air is forced past the evaporator coil 14, cooled, and returned to the building.

With reference now to FIG. 2, the inside unit 26 of the present invention is shown. The inside unit 26 comprises a freeze-up sensor 30, a vacuum sensor 32, and a sensor monitor 34. The freeze-up sensor 30 is positioned proximate the evaporator coil 14 and adapted to determine whether an air temperature within the inside unit 26 proximate the evaporator coil is near a threshold temperature. The freeze-up sensor 30 may comprise an electronic or mechanical sensor capable of detecting air temperature. Preferably, the freeze-up sensor 30 is capable of detecting both an air temperature and condensation. When the freeze-up sensor 30 detects a threshold temperature near freezing, it sends a freeze-up signal to the sensor monitor 34. Preferably, the freeze-up sensor 30 sends the freeze-up signal to the sensor Monitor 34 when a temperature below 35 degrees Fahrenheit is detected and more preferably when a temperature below 30 degrees Fahrenheit is detected. One freeze-up sensor 30 which may be used is a cooling coil temperature sensor having a temperature sensitivity of two degrees Celsius.

The vacuum sensor 32 is adapted to detect a vacuum pressure within the HVAC system 10. A vacuum pressure in excess of a threshold pressure can cause the blower 20 to work harder and ultimately fail. The vacuum sensor 32 is adapted to transmit a vacuum signal to the sensor monitor 34 when the threshold pressure is reached. Preferably, the threshold pressure at which the vacuum sensor transmits the vacuum signal is adjustable. The vacuum sensor 32 may be any one of a number of commercially available pressure sensors. One particular vacuum sensor 32 that can be used is an external fan box differential pressure sensor, having a 2 inHg pressure range, though other sensors can be used. As shown in FIG. 2, the vacuum sensor 32 is located proximate the filter 28.

Continuing with FIG. 2, the freeze-up sensor 30 and the vacuum sensor 32 are operatively connected to the sensor monitor 34 such that the sensor monitor can detect whether the freeze-up sensor 30 is transmitting a freeze-up signal and/or the vacuum sensor 32 is transmitting a vacuum signal. The sensor monitor 34 transmits an indicator signal to an indicators 36 a and 36 b located proximate the thermostat 22. In the embodiment shown in FIG. 2, the indicators 36 a and 36 b comprise a vacuum monitor light 36 a, and a freeze-up monitor light 36 b. The vacuum monitor light 36 a is illuminated when the vacuum sensor 32 is transmitting a vacuum signal, and the freeze-up monitor light 36 b is illuminated when the freeze-up sensor 30 is transmitting the freeze-up signal.

In a preferred embodiment, the sensor monitor 34 further comprises a processor (not shown) programmed to determine which of the freeze-up monitor light 36 a and the vacuum monitor light 36 b was activated first. The processor may activate an additional light, or a setting recorded in the memory of the sensor monitor 34 or the indicator 36. Thus, a technician or occupant could determine the cause of problems with the HVAC system 12 and more efficiently address the problem.

With reference to FIG. 3, the HVAC system 12 may further comprise a switch 50 operatively connected to the sensor monitor 34 and to the outside unit 24. The switch 50 is usually open, such that in normal operation of the HVAC system 12, components of the outside unit 24 such as the compressor 18 and condenser 16 operate normally. However, when the sensor monitor 34 receives the freeze-up signal or the vacuum signal, the switch 50 closes, causing the condenser 16 and compressor 18 to shut off, preventing damage to the HVAC system 12. When the sensor monitor 34 no longer receives the freeze-up signal or the vacuum signal, the switch 50 re-opens, allowing some limited non-destructive operation of the HVAC system 12 even when a defective condition may still exist. The indicators 36 a or 36 b located at thermostat 22 (FIG. 2) indicate whether the switch 50 has deactivated the compressor 18 and condenser 16.

The thermostat 22 may be any of a number of commercially available thermostats, and adapted for use with the indicators 36 a and 36 b of the apparatus 10. With reference now to FIG. 4, an improved embodiment of the thermostat 22 for use in the present invention is shown in more detail. The thermostat 22 comprises a chassis 101 to support a touch screen display 100. Preferably, the touch screen display 100 is a resistive interface compatible with a finger and/or stylus (not shown). The touch screen display 100 comprises a continuous setpoint graph 102 for programming a temperature. The continuous setpoint graph 102 is adjustable on the touch screen display 100 and may be used to create a continuous temperature setpoint for operation of the HVAC system 12 over an extended period of time. Multiple functions of the thermostat 22 and HVAC system 12 may be adjusted at the touch screen display 100, such as the time, threshold temperature for the freeze-up sensor 30 (FIG. 2), threshold pressure for the vacuum sensor 32 (FIG. 2), and other operational and automated functions. Further, the thermostat 22 contains a memory device (not shown) which allows data logging and updating of the thermostat software. The touch screen display 100 may further comprise a control interface 104 to control operation of the HVAC system 12, an internal clock, the blower fan 20 (FIG. 1), and settings such as Fahrenheit reading vs. Celsius reading and display language. Additionally, the thermostat 22 may comprise a battery backup in the case of external power failure. As shown, the indicators 36 a and 36 b may be integral with the thermostat 22, and the freeze-up monitor indicator 36 a and vacuum monitor indicator 36 b are located on the touch screen display 100.

In operation, the apparatus 10 is used to provide a method for monitoring the HVAC system 12. First, the freeze-up sensor 30 detects temperature and the presence of condensation proximate the evaporator coil 14. When the threshold temperature is detected, the freeze-up sensor 30 transmits a freeze-up signal to the sensor monitor 34. After receiving the freeze-up signal, a processor (not shown) located at the thermostat 22 transmits a shutdown signal to the compressor 18 and/or the condenser 16. Finally, operation of the compressor 18 and condenser 16 may resume when the freeze-up signal is no longer received by the sensor monitor 34.

The vacuum sensor 32 may also transmit a vacuum signal when the vacuum sensor 32 indicates a threshold vacuum pressure proximate the filter 28. The filter 28 may be replaced with a clean filter if the filter is viewed as the cause of the problem, for example, if the vacuum signal was transmitted prior to the freeze-up signal. A desired vacuum pressure at which the vacuum sensor 32 transmits the vacuum signal may be set at the thermostat 22. The thermostat 22 may also allow an occupant to set a continuous temperature setpoint 102.

Various modifications in the design and operation of the present invention are contemplated without departing from the spirit of the invention. For example, the apparatus 10 and HVAC unit 12 may be operated remotely, or through Internet access. Thus, while the principal preferred construction and modes of operation of the invention have been illustrated and described in what is now considered to represent its best embodiments it should he understood that the invention may be practiced otherwise than as specifically illustrated and described. 

1. An apparatus for monitoring a HVAC system, the HVAC system comprising a thermostat, a condensing unit, a compressor, an evaporator coil, and a filter, the apparatus comprising: a freeze-up sensor located proximate the evaporator coil such that when the sensor detects a threshold temperature the sensor transmits a freeze-up signal; a receiver for receiving the freeze-up signal; a switch operatively connected to the HVAC system and the receiver to disable the compressor and condensing unit after the freeze-up signal is received by the receiver; an indicator located proximate the thermostat indicating receipt of the freeze-up signal by the receiver.
 2. The apparatus of claim 1 further comprising a vacuum sensor located proximate the filter to detect a threshold vacuum pressure and transmit a vacuum signal to the receiver upon detection of a vacuum pressure at or exceeding the threshold vacuum pressure.
 3. The apparatus of claim 2 further comprising a screen located proximate the thermostat comprising: a touch screen display; the indicator; and a continuous setpoint graph located at and adjustable on the touch screen display for creating a continuous temperature setpoint.
 4. The apparatus of claim 1 wherein the threshold temperature is less than 35 degrees Fahrenheit.
 5. The apparatus of claim 1 wherein the freeze-up sensor is adapted to detect condensation proximate the evaporator coil.
 6. An apparatus for monitoring a HVAC system, the HVAC system comprising a thermostat, a condensing unit, a compressor, an evaporator coil, and a filter, the apparatus comprising: a freeze-up sensor located proximate the evaporator coil such that when the sensor detects a threshold temperature and condensation proximate the evaporator coil the freeze-up sensor transmits a freeze-up signal; a vacuum sensor located proximate the filter to transmit a vacuum signal upon detection of a vacuum pressure at or exceeding a threshold vacuum pressure; a receiver for receiving the freeze-up signal and the vacuum signal; a switch to disable the compressor and condensing unit after the receiver receives the freeze-up signal or the vacuum signal; and an indicator located proximate the thermostat indicating the switch has disabled the compressor and condensing unit.
 7. The apparatus of claim 6 wherein the receiver is proximate the thermostat.
 8. The apparatus of claim 6 wherein the receiver comprises a sensor monitor.
 9. The apparatus of claim 6 wherein the indicator indicates whether the freeze-up signal or the vacuum signal occurred first.
 10. A method for monitoring an HVAC system, the HVAC system comprising a thermostat, a condensing unit, a compressor, an evaporator coil, and a filter, the method comprising: detecting a threshold temperature and condensation proximate the evaporator coil; transmitting a freeze-up signal after detection of the threshold temperature and condensation proximate the evaporator coil; receiving the freeze-up signal at a receiver; transmitting a shut-down signal to the compressor and condensing unit upon receipt of the freeze-up signal at the receiver; ceasing operation of the compressor and condensing unit after receiving the freeze-up signal; and resuming operation of the compressor and condensing unit when the freeze-up signal is no longer received by the receiver.
 11. The method of claim 10 further comprising transmitting a vacuum signal when the vacuum sensor indicates a vacuum pressure at or exceeding a threshold vacuum pressure proximate the filter.
 12. The method of claim 11 further comprising adjusting the threshold vacuum pressure at which the vacuum-sensor transmits a vacuum signal.
 13. The method of claim 11 further comprising detecting which of the vacuum signal and the freeze-up signal was transmitted first.
 14. The method of claim 13 further comprising replacing the filter if the vacuum signal was transmitted prior to the freeze-up signal.
 15. The method of claim 10 further comprising setting a continuous temperature setpoint at the thermostat.
 16. A thermostat for use with an HVAC system comprising a filter, the thermostat comprising: a touch screen display; a freeze-up indicator located on the touch screen display and operatively connected to a freeze-up sensor; a vacuum indicator located on the touch screen display and operatively connected to a vacuum sensor; wherein the freeze-up indicator indicates the HVAC system is not operating due to a low temperature and condensation in the HVAC system and the vacuum sensor indicates the HVAC system is not operating due to a vacuum pressure at or exceeding a threshold pressure in the HVAC system; and a continuous setpoint graph located at and adjustable on the touch screen display for creating a continuous temperature setpoint. 